JPH0747209Y2 - Vehicle suspension controller - Google Patents

Description

[Detailed Description of the Invention] [Industrial application] The present invention relates to a suspension control device for a vehicle, and more particularly, to a damping force of the suspension device when the nose dive amount increases due to sudden stop of the vehicle. By switching the characteristics to the hard side, the rolling back as a reaction of the nose dive of the vehicle in the sudden braking stop state is suppressed and the switching operation of unnecessary damping force is eliminated to reduce the switching frequency, and the switching mechanism The present invention relates to a vehicle suspension control device capable of reducing the power consumption of the vehicle, alleviating the demand for durability of the switching mechanism, and consequently reducing the cost.

[Conventional technology]

As a conventional vehicle suspension control device, for example, one disclosed in Japanese Patent Laid-Open No. 58-30816 is known.

This conventional device is incorporated in a hydraulic shock absorber, and a variable orifice whose flow cross-sectional area can be adjusted small to set the damping force of the shock absorber to the hard side, and the flow cross-sectional area of the variable orifice. The solenoid incorporated in the shock absorber to change the pressure, the brake hydraulic switch that detects the hydraulic pressure of the brake system, and the variable orifice by supplying the exciting current to the solenoid during sudden braking based on the detection signal of the brake hydraulic switch. And a control circuit for reducing the flow cross-sectional area of the vehicle, and the damping force of the shock absorber is set to the hard side during the sudden braking of the vehicle, thereby suppressing the so-called nose dive during the rapid braking. .

Further, as another conventional device, one disclosed in Japanese Patent Application Laid-Open No. 60-4406 related to the application of the present applicant is also known.

This conventional device is provided with a vehicle speed sensor that outputs a signal corresponding to the vehicle speed of the vehicle, detects the vehicle speed of the vehicle from the vehicle speed signal, and the vehicle speed value is equal to or less than a predetermined set value, so the vehicle stops. It is equipped with a control mechanism that outputs a switching signal that switches the damping force of the shock absorber to the hard side when it detects that the vehicle is traveling at medium or low speed, and the damping force of the shock absorber is reduced when the vehicle is stopped or at low speed. By switching to the hard side, the nose dive of the vehicle and the swinging back as a reaction thereof are suppressed.

[Problems to be solved by the invention]

However, in the former conventional device described above, the sudden braking state is determined based on the detection signal of the brake oil pressure switch, and the damping force of the shock absorber is switched to the hard side based on this determination. Although the nose dive of can be suppressed, the damping force of the shock absorber is switched to the hard side based on the detection signal of the brake hydraulic switch, so when the braking is released, the damping force of the shock absorber becomes the soft side and braking is performed. There is a problem in that it is not possible to suppress the swing-back as a reaction of the nose dive that occurs when the lock is released.

Further, in the latter conventional device, the damping force is constantly switched to the hard side when it is determined that the vehicle is stopped or traveling at a low speed, so that the swing-back at the time of stopping is large. Switching is performed not only during expected sudden braking, but also when swinging back is small at the time of stopping, such as when stopping with gentle braking, and therefore when it is considered unnecessary to switch the damping force to the hard side. However, there has been a problem that the frequency of switching is increased, the power consumption of the switching mechanism is increased, the durability of the switching mechanism is required more than necessary, and eventually the cost is increased.

The present invention was made in view of such conventional problems, and suppresses swinging back as a reaction of the nose dive during sudden braking of the vehicle and eliminates unnecessary switching operation of damping force. An object of the present invention is to provide a suspension control device for a vehicle that can reduce the frequency of switching, reduce the power consumption of the switching mechanism, alleviate the requirement for durability of the switching mechanism, and eventually reduce the cost. It is a thing.

[Means for solving problems]

Therefore, as shown in FIG. 1, a suspension control device for a vehicle according to the present invention is capable of switching the damping force characteristic of a variable damping force shock absorber to at least two stages, a soft side and a hard side, by inputting a switching signal. An apparatus, a braking start vehicle height detecting means for detecting a vehicle height when the vehicle starts braking, a braking stop vehicle height detecting means for detecting a vehicle height when the vehicle is stopped by braking, and a braking start vehicle height detecting means. Nose dive amount calculation means for calculating the difference value between the vehicle height detection value and the vehicle height detection value of the braking stop vehicle height detection means as a nose dive amount, and the nose dive amount of the nose dive amount calculation means is equal to or more than a set value. At one time, it comprises a switching means for switching the damping force characteristic of the suspension device to the hard side.

[Action]

The operation of the suspension control device for a vehicle according to the present invention is such that when the vehicle is in a braking state, the vehicle height at the time of starting the braking is detected by the braking start vehicle height detecting means, and at the time of stopping the vehicle by braking. By detecting the vehicle height by the braking stop vehicle height detecting means, the nose dive amount calculating means,
The nose dive amount actually occurring at the time of braking stop is calculated from the vehicle height change from the start of braking to the stop of braking, and when this nose dive amount is equal to or greater than the set value, the damping force variable shock of the suspension device is changed by the switching means. Switch the damping force characteristics of the absorber to the hard side. For this reason, it is possible to accurately determine the amount of swing-back as a reaction of the nose dive when the vehicle is being braked, suppress this swing-back, and eliminate unnecessary switching operation of the damping force to switch the switching mechanism. It reduces the frequency.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

First, the configuration will be described.

In FIG. 2, 1a and 1b are front wheels, 1c and 1d are rear wheels, and 2
Is an engine and 3 is a transmission.

4 is a brake switch, and this brake switch 4
Is attached in conjunction with a brake pedal (not shown) and outputs a signal that is turned on during braking and turned off during non-braking.

Reference numeral 5 denotes a vehicle speed sensor that generates a vehicle speed pulse for detecting the traveling speed (that is, vehicle speed) of the vehicle. The vehicle speed sensor 5 detects, for example, the rotation speed of a speedometer cable (not shown), or A device that detects the rotational speed of the output shaft of the transmission 3 or the propeller shaft 6 by the contact period of a reed switch or the like is used.

Reference numeral 7 denotes a vehicle height sensor, which is, for example, an ultrasonic distance-measuring type having a transmitter for transmitting ultrasonic waves and a receiver for receiving ultrasonic waves, and is used for a front end of a vehicle body (not shown). It is attached to the lower surface part of the section. The vehicle height sensor 7 provides an output signal according to the distance between the front end of the vehicle body and the road surface immediately below the front end.

Reference numerals 8a to 8d are damping force variable shock absorbers interposed between the wheels 1a to 1d and the vehicle body, and 9 is a controller for switching and adjusting the damping force of the damping force variable shock absorbers 8a to 8d.

FIG. 3 shows, as an example of the damping force variable shock absorbers 8a to 8d, a damping force that can be switched between two steps, soft side and hard side.

In the figure, reference numeral 11 denotes a piston rod formed by connecting an upper rod 12 and a lower rod 13, the upper end of which is fixed to the vehicle body side. 14 is a tube whose lower end is fixed to the wheels 1a to 1d side, 15 is a piston fixed to the lower end of the lower rod 13 and slides along the inner peripheral surface of the tube 14, 16 is a tube 14 at the bottom side of the tube 14. It is a free piston that slides along the inner peripheral surface of. Then, inside the tube 14, above the piston 15, the piston upper chamber A,
A piston lower chamber B is formed between the piston 15 and the free piston 16, a gas chamber C is formed below the free piston 16, and oil is provided in the piston upper chamber A and the piston lower chamber B, respectively.
The gas chamber C is filled with high-pressure gas.

Reference numeral 17 is an expansion side valve, 18 is an expansion side orifice, 19 is a contraction side valve, and 20 is a contraction side orifice. Also, 21 and 22
Is a through hole and a hollow portion formed in the upper rod 12, and 23 and 24 are a bypass passage and a hollow portion formed in the lower rod 13.

A plunger 25 is placed in the two cavities 22 and 24,
The plunger 25 is constantly pressed upward in the drawing (direction D) by a return spring 26, and a solenoid 27 is arranged around the plunger 25. And solenoid 27
Is connected to a drive circuit 29 via a lead wire 28 passing through the through hole 21 of the upper rod 12.

In the damping force variable shock absorbers 8a to 8d, the expansion side valve 17 is opened in the expansion stroke, the piston upper chamber A and the piston lower chamber B are communicated with each other via the expansion side orifice 18, and the compression side valve 19 is connected. Thus, the contraction side orifice 20 is closed. Further, in the compression stroke, the compression valve 19 opens, the piston upper chamber A and the piston lower chamber B communicate with each other via the compression orifice 20, and the expansion valve 18 closes the expansion orifice 18. .

In FIG. 4, the controller 9 comprises a microcomputer 31 and a drive circuit 29 for switching and driving the damping forces of the variable damping force shock absorbers 8a to 8d.
The microcomputer 31 is configured to include at least an interface circuit 32, an arithmetic processing unit 33, and a storage device 34 such as RAM or ROM. The brake switch 4, the vehicle speed sensor 5, the vehicle height sensor 7, and the drive circuit 29 are connected to the interface circuit 32. If the signal from the vehicle height sensor 7 according to the vehicle height value is an analog signal, the vehicle height sensor 7 is connected to the interface circuit 32 via an A / D converter, which is not shown.

The arithmetic processing unit 33 reads the signals from the brake switches 4, the vehicle speed sensor 5 and the vehicle height sensor 7 via the interface circuit 32, and performs the arithmetic processing described later based on these signals. The storage device 34 stores a predetermined program necessary for executing the arithmetic processing, and the arithmetic processing device.
The calculation result of 33 is stored.

Next, the operation of this embodiment will be described.

A signal from the brake switch 4 that is turned on during braking and turned off during non-braking, a pulse signal from the vehicle speed sensor 5 according to the vehicle speed value V, and the distance between the vehicle body front end from the vehicle height sensor 7 and the road surface immediately below it. That is, a signal corresponding to the vehicle height value H is supplied to the interface circuit 32 of the microcomputer 31.

FIG. 5 is a flowchart showing a procedure of processing executed in the microcomputer 31, and FIG. 6 is a vehicle based on a signal from the brake switch 4, a vehicle speed value V based on a signal from the vehicle speed sensor 5, and a detection signal from the vehicle height sensor 7. It is a time chart which shows the state of high value H and damping force of damping force variable shock absorbers 8a-8d.

In FIG. 5, in step, it is checked whether or not the brake flag is "1". This brake flag is
Initially, it is set to "0", and as will be described later, it is reset to "0" after completion of the swing-back control of the present invention. In the state where the vehicle is running and the braking operation is not performed (initial T _{1 in} FIG. 6), the brake flag is “0” in step.
Therefore, the process proceeds to the next step and the brake switch 4
It is determined whether the signal from is on. Since the signal from the brake switch 4 is off during the period T ₁ , the process returns without performing any processing. At this time, the damping forces of the damping force variable shock absorbers 8a to 8d are set to the soft side in the normal state.

When the damping forces of the variable damping shock absorbers 8a to 8d are set to the soft side, the interface circuit 32 of the microcomputer 31 sends a switching signal of "L (low level or logical value" 0 ")" to the drive circuit 29. Supply. Thus, in FIG. 3 and FIG. 4, the exciting current is not supplied from the drive circuit 29 to the solenoid 27, the solenoid 27 is de-energized, and the plunger 25 becomes the return spring 26.
The upper end of the plunger 25 is disengaged from the bypass passage 23 by the urging force of the
The piston upper chamber A and the piston lower chamber B are brought into communication with each other via the. Therefore, the damping force variable shock absorbers 8a to 8d
The damping force of is set to the soft side.

Returning to FIG. 5, when the signal from the brake switch 4 is turned on in the step, this is the time t1 when the braking is started in FIG. In this case, the brake flag "1" the process proceeds to step and then proceeds to step, from the detection signal of the vehicle height sensor 7 reads the vehicle height H ₁ of the vehicle front end, the process returns.

In the next processing cycle, the brake flag is "1" at the step, so the routine proceeds to the step and it is checked whether or not the stop flag is "1". This stop flag is also set to "0" by default, and as will be described later,
It is reset to "0" after completion of the swing-back control of this invention, and is "0" in the processing cycle immediately after time t1.
Is. Therefore, the process proceeds to the next step, and it is determined whether or not the vehicle is in a stopped state. For this determination, a signal corresponding to the vehicle speed value V based on the detection signal from the vehicle speed sensor 5 is read. If V ≠ 0, the vehicle is not stopped (that is, the vehicle is running), and if V = 0, the vehicle is stopped. To determine. In the processing cycle immediately after the time point t1, the vehicle is in the traveling state, so the processing returns without performing any processing. At this time, the damping forces of the variable damping force shock absorbers 8a to 8d are maintained on the soft side. The process of repeating the step ---- return is continued during the period T ₂ shown in FIG.
During this period T ₂ , the braking operation is in progress, and the vehicle speed value V decreases.

Eventually, when the vehicle speed value V = 0 in the step, this becomes the time point t2 shown in FIG. 6 when the vehicle stops. In this case, move to the next step and set the stop flag to "1", then move to the step and read the vehicle height value H ₂ from the detection signal of the vehicle height sensor 7, then move to the step,
It reads the vehicle height H ₁ of the brake start time t1 read in the step, obtaining the difference value ΔH = H ₁ -H _2. This difference value represents the nose dive amount at the vehicle stop time t2. Next, move to the step, and this nose dive amount Δ
Compare H with a predetermined reference value ΔH ₀ .

If ΔH ≧ ΔH ₀ in the step, it is determined that the nose dive amount is large and the vehicle has stopped due to sudden braking, and then the process proceeds to the step to switch the damping force to the hard side for the predetermined time T _0. Set the timer of T to T ₀ and return.

In the next processing cycle, the vehicle stop flag is "1" at the step, so the routine proceeds to the next step to count down the timer and then proceeds to the step to check whether the timer value is 0 or not. . Since the timer is> 0 in the processing cycle immediately after the time point t2, the step moves to the next step and the damping forces of the variable damping force shock absorbers 8a to 8d are switched to the hard side.

When switching the damping forces of the variable damping force shock absorbers 8a to 8d to the hardware side, the interface circuit 32 of the microcomputer 31 supplies a switching signal of "H (high level or logical value" 1 ")" to the drive circuit 29. To do. By doing so, in FIG. 3 and FIG. 4, the excitation current of a predetermined value is supplied from the drive circuit 29 to the solenoid 27 to cause the solenoid 27 to move.
Is excited, the electromagnetic force of the solenoid 27 moves the plunger 25 downward in the drawing (direction E) against the urging force of the return spring 26, and the bypass passage 23 is closed. Therefore, the damping forces of the variable damping force shock absorbers 8a to 8d are switched to the hard side.

Returning to FIG. 5, the damping force is maintained on the hard side as long as the timer> 0 in the step, and when the timer = 0 in the step, the process proceeds to the next step and the damping force is returned to the soft side. Therefore, the damping force is set on the hard side only for the predetermined time T ₀ set by the timer, and during this period, the swingback as a reaction of the large nose dive is suppressed. After the damping force is returned to the soft side in step, the process shifts to step, the brake flag and the vehicle stop flag are reset to "0", and the process returns.

When it is determined in step that the nose dive amount ΔH <ΔH ₀ at the vehicle stop time t2, it is determined that the braking operation is gentle braking, and it is not necessary to switch the damping force to the hard side, and the processing is performed. Return without doing anything (that is, without setting the timer). Therefore, in the next processing cycle, the timer does not count down in the step,
In the step, the timer = 0, and in the step, the brake flag and the stop flag are reset to "0" while the damping force is maintained on the soft side as before.

Therefore, in the process of the present invention shown in FIG. 5, the damping force variable shock absorbers 8a to 8d are provided only when the vehicle stops due to sudden braking and the nose dive amount is equal to or greater than a predetermined value.
The damping force of is switched to the hard side, and other than that, the damping force is maintained on the soft side, including the case of the stop due to the slow braking.

In FIG. 6, the three curves representing the vehicle height value H are broken lines F ₁
Shows the case where the nose dive amount ΔH is small and the damping force is not switched to the hard side but remains on the soft side. Solid line F ₂
Indicates a case where the nose dive amount ΔH is large but the damping force remains on the soft side without being switched to the hard side. In this case, the swing back as a reaction of the nose dive is large. The alternate long and short dash line F ₃ shows the control of this invention, and it can be seen that the swing back is effectively suppressed.

In addition, in FIGS. 1, 4, and 5, the brake switch 4 and the steps 1 to 4 are specific examples of the braking start vehicle height detecting means, and the steps 1 to 4 are specific examples of the braking stop vehicle height detecting means. , A specific example of the nose dive amount calculating means, and a specific example of the driving circuit 29 and the switching means in the steps 1 to 3 are shown. Also, as the vehicle height sensor, an ultrasonic distance measuring type is exemplified,
It may be of a type that detects the relative displacement between the vehicle body and the wheels.

Further, the damping force characteristic is exemplified as one that can be switched between two steps of the soft side and the hard side, but for the one that can be switched in multiple steps of three steps or more, the present invention is applied to appropriate two steps among them. be able to.

Further, although the case where the microcomputer is used as the controller is illustrated, the electronic circuit such as the subtraction circuit, the comparison circuit, the logic circuit, and the command value setting circuit may be combined instead.

[Effect of device]

As described above, according to the vehicle suspension control device of the present invention, the vehicle is stopped due to sudden braking,
Only when the nose dive amount at that time is large, the damping force characteristic of the variable damping force shock absorber is switched to the hard side, so it is possible to suppress the rolling back as a reaction of the nose dive of the vehicle in the sudden braking stop state. In addition, it is possible to eliminate unnecessary switching operation of the damping force, reduce the switching frequency, reduce the power consumption of the switching mechanism, reduce the durability requirement of the switching mechanism, and eventually reduce the cost. The effect of being able to be obtained is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of a vehicle suspension control device according to the present invention, FIG. 2 is a perspective view showing the overall configuration of an embodiment of the present invention, and FIG. 3 is an example of a variable damping force shock absorber. FIG. 4 is a longitudinal sectional view showing
FIG. 5 is a block diagram showing details of the embodiment shown in the figure, FIG. 5 is a flow chart showing a processing procedure executed in the microcomputer, and FIG. 6 is a time chart showing the operation of the embodiment. 1a 1d …… Wheels, 4 …… Brake switch, 5 …… Vehicle speed sensor, 7 …… Vehicle height sensor, 8a 8d …… Variable damping force shock absorber, 9 …… Controller, 11 …… Piston rod, 14 …… Tube , 15 …… Piston, 23 …… Bypass passage, 25 …… Plunger, 26 …… Return spring, 27 …… Solenoid, 29 …… Drive circuit, 31 …… Microcomputer, 32 …… Interface circuit, 33 …… Computation Processor, 34 ... Storage device.

Claims (1)

[Scope of utility model registration request] 1. A suspension device capable of switching the damping force characteristic of a variable damping force shock absorber into at least two stages, a soft side and a hard side, by inputting a switching signal, and a braking start for detecting a vehicle height at the start of braking of the vehicle. Vehicle height detection means, braking stop vehicle height detection means for detecting vehicle height when the vehicle is stopped by braking, vehicle height detection value of the braking start vehicle height detection means, and vehicle height detection of the braking stop vehicle height detection means A nose dive amount calculating means for calculating a difference value from the value as a nose dive amount, and when the nose dive amount of the nose dive amount calculating means is a set value or more, the damping force characteristic of the suspension device is switched to the hard side. A suspension control device for a vehicle, comprising a switching means.